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oai:ojs.www.eurjchem.com:article/638 2012-12-31T23:10:35Z eurjchem:ART driver

Theoretical density functional study of gas-phase tautomerization and acidity of 5-methylhydantoin and its thio derivatives Safi, Zaki Sulieman DFT B3LYP Acidity Deprotonation Tautomerization 5-Methylhydantoin Tautomerization and acidities of various 5-methylhydantoins and their thio derivatives were predicted using Density Functional Theory (DFT). The functional used was B3LYP and the basis set for all atoms was 6-311+(d,p). Single point energy computations were performed at the 6-311+G(2df,2p) basis set. The relative stabilities of the different tautomers of the 2,4-dioxo, 2-thio-4-oxo, 4-thio-2-oxo and 2,4-dithio derivatives of the deprotonated 5-methylhydantoin have been studied. In all cases, the most stable deprotonated conformers are the oxo-thione, the dioxo or the dithio. As for the neutral and the protonated 5-methylhydantoin-thio derivatives, the tautomerization activation barriers are high enough as to conclude that the oxo-thione structures should be found in the gas phase. It was revealed that the ring-nitrogen atom at position 3 (N3) is more acidic than that at position 1 (N1), hence 5-methylhydantoin thio derivatives in the gas phase are an N3-acid. It has been found that the 2,4-dithio species is the most acidic compound among all the investigated compounds. The acidity values were found to be 343 (2O4O), 337 (2S4O), 336 (2O4S) and 332 kcal/mol (2S4S). Atlanta Publishing House LLC 2012-09-30 info:eu-repo/semantics/article info:eu-repo/semantics/publishedVersion application/pdf https://www.eurjchem.com/index.php/eurjchem/article/view/638 10.5155/eurjchem.3.3.348-355.638 European Journal of Chemistry; Vol. 3 No. 3 (2012): September 2012; 348-355 2153-2257 2153-2249 eng https://www.eurjchem.com/index.php/eurjchem/article/view/638/PDF